Experimental and numerical investigations on adhesively bonded timber joints

Adhesively bonding of timber structural elements provides new opportunities as it is well adapted for the anisotropic and fibrous nature of the material. Experimental and numerical investigations were carried out on adhesively bonded full-scale double-lap joints composed of timber adherends (spruce) and adhesive layers. The influence of different geometric parameters and adhesives on the joint strength was studied. The investigated geometric parameters were the thickness of the adhesive layer (0.5–2.0?mm), the overlap length (40–280?mm), and the ductility of the adhesive (using three different adhesives). It was found that the joint strength was independent of the adhesive layer thickness (for the thickness range investigated) that the joint strength increased with the overlap length up to an apparent maximum of approximately 200?mm and that strength was almost independent of the adhesive stiffness. The numerical investigation was in good agreement with the experimental results and allows for the model to be used for strength prediction of the investigated joints.     

Analysis of runoff,sediment dynamics and sediment yield of subcatchments in the highly erodible Isábena catchment,Central Pyrenees

Purpose

The Isábena catchment (445 km²), Spain, features highly diverse spatial heterogeneity in land use, lithology and rainfall. Consequently, the relative contribution in terms of water and sediment yield varies immensely between its subcatchments, and also temporally. This study presents the synthesis of ~2.5 years of monitoring rainfall, discharge and suspended sediment concentration (SSC) in the five main subcatchments of the Isábena and its outlet.

Materials and methods

Continuous discharge at the subcatchment outlets, nine tipping bucket rainfall and automatic SSC samplers (complemented by manual samples), were collected from June 2011 until November 2013. The water stage records were converted to discharge using a rating curve derived with Bayesian regression. For reconstructing sediment yields, the data from the intermittent SSC sampling needed to be interpolated. We employed non-parametric multivariate regression (Quantile Regression Forests, QRF) using the discharge and rainfall data plus different aggregation levels of these as ancillary predictors. The subsequent Monte Carlo simulations allowed the determination of monthly sediment yields and their uncertainty.

Results and discussion

The stage–discharge rating curves showed wide credibility intervals for the higher stages, with great uncertainties associated with the discharge rates, especially during floods. The water yield of the subcatchments differed considerably. The entire catchment’s output was dominated by the northernmost subcatchment (~360 mm year^?1). The smaller, southern subcatchments featured much higher variability and lower runoff rates (55–250 mm year^?1). The SSCs exhibited a wide range and can exceed 100 g l^?1 for the central subcatchments, where most of the badlands are located. For the reconstruction of the sedigraphs, the QRF method proved suitable with Nash–Sutcliffe indices of 0.50 to 0.84. The specific sediment yield ranges from relatively low (32 t km^?2 year^?1) in the highly vegetated north to high values (3,651 t km^?2 year^?1) in areas with many badland formations.

Conclusions

The Isábena catchment shows high erosion dynamics with great variability in space and time, with stark contrasts even between adjacent subcatchments. The natural conditions make water and sediment monitoring and instrumentation very challenging; the measurement of discharge is particularly prone to considerable uncertainties. The QRF method employed for reconstructing sedigraphs and monthly yields proved well suited for the task.     

Differential effect of elicitors on biphenyl and dibenzofuran formation in Sorbus aucuparia cell cultures

The Rosaceous subtribe Pyrinae (formerly subfamily Maloideae) is well-known for its economically important fruit trees, such as apple and pear, and also includes Sorbus aucuparia. Elicitor-treated S. aucuparia cell cultures are used to study the biosynthesis of the Pyrinae-specific phytoalexins, biphenyls and dibenzofurans. Three biphenyls (aucuparin, noraucuparin, 2'-hydroxyaucuparin) and a dibenzofuran (eriobofuran) were isolated and structure elucidated using GC-MS and NMR. A second dibenzofuran of low abundance was tentatively assigned as noreriobofuran. Treatment of S. aucuparia cell cultures with yeast extract induced the formation of aucuparin as the major phytoalexin. In contrast, addition of preparations from the fire blight bacterium, Erwinia amylovora, and the scab-causing fungus, Venturia inaequalis, resulted in accumulation of eriobofuran as the major inducible constituent. Methyl jasmonate was a poor elicitor. The observations are suggestive of a biogenic relationship between biphenyls and dibenzofurans. Elicitor-treated S. aucuparia cell cultures provide an interesting in vitro system for studying biphenyl and dibenzofuran metabolism in the economically valuable Pyrinae.     

In-depth mechanistic study on the formation of acrylamide and other vinylogous compounds by the maillard reaction

The formation of acrylamide was studied in low-moisture Maillard model systems (180 degrees C, 5 min) based on asparagine, reducing sugars, Maillard intermediates, and sugar degradation products. We show evidence that certain glycoconjugates play a major role in acrylamide formation. The N-glycosyl of asparagine generated about 2.4 mmol/mol acrylamide, compared to 0.1-0.2 mmol/mol obtained with alpha-dicarbonyls and the Amadori compound of asparagine. 3-Hydroxypropanamide, the Strecker alcohol of asparagine, generated only low amounts of acrylamide ( approximately 0.23 mmol/mol), while hydroxyacetone increased the acrylamide yields to more than 4 mmol/mol, indicating that alpha-hydroxy carbonyls are much more efficient than alpha-dicarbonyls in converting asparagine into acrylamide. The experimental results are consistent with the reaction mechanism based on (i) a Strecker type degradation of the Schiff base leading to azomethine ylides, followed by (ii) a beta-elimination reaction of the decarboxylated Amadori compound to afford acrylamide. The beta-position on both sides of the nitrogen atom is crucial. Rearrangement of the azomethine ylide to the decarboxylated Amadori compound is the key step, which is favored if the carbonyl moiety contains a hydroxyl group in beta-position to the nitrogen atom. The beta-elimination step in the amino acid moiety was demonstrated by reacting under low moisture conditions decarboxylated model Amadori compounds obtained by synthesis. The corresponding vinylogous compounds were only generated if a beta-proton was available, for example, styrene from the decarboxylated Amadori compound of phenylalanine. Therefore, it is suggested that this thermal pathway may be common to other amino acids, resulting under certain conditions in their respective vinylogous reaction products.     

Long-term management impacts on soil C, N and physical fertility: Part I: Broadbalk experiment

For many centuries manure application to the soil has been common practice. Organic amendments and fertiliser applications can increase crop yields and soil organic matter (SOM). However, the long-term impacts on soil physical fertility are often neglected. This study was carried out on the Broadbalk Wheat Experiment at Rothamsted, UK, established in 1843 on an Aquic/Typic Paleudalf soil. Application of farmyard manure (FYM), N fertiliser and wheat straw on total organic C (C_T), labile C (C_L) and non-labile C (C_NL), total N (N_T), mean weight diameter (MWD) and unsaturated hydraulic conductivity (K_unsat) were studied on wheat (Triticum aestivum) and adjacent woodland and pasture areas. Manure additions, N fertiliser and straw incorporation increased all C fractions, particularly the C_L fraction. The addition of 35 t ha⁻¹ year⁻¹ of FYM increased C_T to 2.5 times that of the control (no fertiliser) treatment and C_L to 5 times that of the control. With highest N application and straw returned, C_T increased by 1.3 times and C_L by 1.5 times that of the control treatment. There were linear relationships between rate of N fertiliser applied and all C fractions, with the rate of increase almost double with straw than straw removed. Manure application improved MWD, as did high N fertiliser additions with straw returned. Application of N fertiliser only increased MWD and K_unsat (at 10 mm tension) if straw was returned, while the addition of manure resulted in decreased K_unsat. The highest K_unsat rate was on the high N fertiliser, straw returned treatments. The uncropped areas all had high soil structural stability. Similar relationships occurred between all C fractions and N_T and MWD for the high C soils, but relationships were much stronger with C_L than the other C fractions in the low C soils. These results showed that soils with low C concentration are more reliant on C_L for structural stability.     

Availability of P from 32P-labelled endogenous soil P and 33P-labelled fertilizer in an alkaline soil producing cotton in Australia

Yield responses of irrigated, field‐grown cotton to phosphorus fertilizer application in Australia have been variable. In an attempt to understand better this variability, the distribution of fertilizer P within soil P fractions was identified using ³²P and ³³P radioisotopes. The soil chosen, an alkaline, grey, cracking clay (Vertosol), was representative of those used for growing cotton in Australia. Chang and Jackson fractionation of soil P from samples collected within 1 h of application indicated that 49, 7 and 13% of the P fertilizer was present as 0.5 m NH₄F, 0.1 m NaOH and 1 m H₂SO₄ extractable P, respectively. Over 89% of the P fertilizer was recovered as Colwell extractable P in these samples, suggesting that the majority of these reaction products was in a highly plant‐available form. Fertilizer‐P remained in an available form within the band 51 days after application, and 68% of the applied fertilizer‐P was recovered as Colwell‐P (1071 mg kg^?1). The Colwell‐P concentration in the band was 35 times that in the unfertilized soil. Thus, the variability in crop response to P fertilizer application in these soils is not a consequence of fertilizer‐P becoming unavailable to plants. These results confirm the suitability of the Colwell (1963) sodium bicarbonate extraction method for measuring available P in these soils.     

The realisable potential supply of woody biomass from forests in the European Union

Forests are important for providing wood for products and energy and the demand for wood is expected to increase. Our aim was to estimate the potential supply of woody biomass for all uses from the forests in the European Union (EU), while considering multiple environmental, technical and social constraints.The potential woody biomass supply was estimated for the period 2010-2030 for stemwood, residues (branches and harvest losses), stumps and other biomass (woody biomass from early thinnings in young forests). We estimated the theoretical biomass potential from recent, detailed forest inventory data using the EFISCEN model. Constraints reducing the availability of woody biomass were defined and quantified for three mobilisation scenarios (high, medium, low). Finally, the theoretical potentials from EFISCEN were combined with the constraints to assess the realisable potential from EU forests.The realisable potential from stemwood, residues, stumps and other biomass was estimated at 744 million m³ yr⁻¹ overbark in 2010 and could range from 623 to 895 million m³ yr⁻¹ overbark in 2030, depending on the mobilisation scenario. These potentials represented 50-71% of the theoretical potential. Constraints thus significantly reduced the biomass potentials that could be mobilised. Soil productivity appeared to be an important environmental factor when considering the increased use of biomass from forests. Also the attitude of private forest owners towards increased use of forest biomass can have an important effect, although quantifying this is still rather difficult.The analysis showed that it is possible to increase the availability of forest biomass significantly beyond the current level of resource utilisation. Implementing these ambitious scenarios would imply quite drastic changes in forest resource management across Europe.     

Sustainable Low-Volume Analysis of Environmental Samples by Semi-Automated Prioritization of Extracts for Natural Product Research (SeaPEPR)

The discovery of novel natural products (NPs) that will serve as lead structures has to be an ongoing effort to fill the respective development pipelines. However, identification of NPs, which possess a potential for application in e.g., the pharma or agro sector, must be as cost effective and fast as possible. Furthermore, the amount of sample available for initial testing is usually very limited, not least because of the fact that the impact on the environment, i.e., the sampled biosystem, should be kept minimal. Here, our pipeline SeaPEPR is described, in which a primary bioactivity screening of crude extracts is combined with the analysis of their metabolic fingerprint. This enabled prioritization of samples for subsequent microfractionation and dereplication of the active compounds early in the workflow. As a case study, 76 marine sponge-derived extracts were screened against a microbial screening panel. Thereunder, human pathogenic bacteria (Escherichia coli ATCC35218 and Staphylococcus aureus ATCC33592) and yeast (Candida albicans FH2173), as well as the phytopathogenic fungus Septoria tritici MUCL45407. Overall, nine extracts revealed activity against at least one test organism. Metabolic fingerprinting enabled assigning four active extracts into one metabolic group; therefore, one representative was selected for subsequent microfractionation. Dereplication of the active fractions showed a new dibrominated aplysinopsin and a hypothetical chromazonarol stereoisomer derivative. Furthermore, inhibitory activity against the common plant pest Septoria tritici was discovered for NPs of marine origin.     

Robust fitting of fluorescence spectra for pre-symptomatic wheat leaf rust detection with Support Vector Machines

Early recognition of pathogen infection is of great relevance in precision plant protection. Pre-symptomatic disease detection is of particular interest. By use of a laserfluoroscope, UV-light induced fluorescence data were collected from healthy and with leaf rust inoculated wheat leaves of the susceptible cultivar Ritmo 2-4 days after inoculation under controlled conditions. In order to evaluate pathogen impact on fluorescence spectra 215 wavelengths in the range of 370-800 nm were recorded. The medians of fluorescence signatures suggest that inoculated leaves may be separated from healthy ones, but high-frequency oscillations and individual reactions of leaves indicate that separability is difficult to achieve. The misbalance between the high number of measured wavelengths and the low number of training examples induces a high overfitting risk. For a pre-symptomatic pathogen identification a small number of robust features was desired which comprise most of the information relevant for the given classification task. Instead of choosing only the most relevant wavelengths, the coefficients of polynomials fitting the spectra were used for classification. They specify the global curve characteristics. Piecewise fitting by polynomials of fourth order led to high classification accuracy. Support Vector Machines were used for classification. Cross validation demonstrated that the achieved classification accuracy reached 93%. This result could be attained on the second day after inoculation, before any visible symptoms appeared. The described method is of general interest for pre-symptomatic pathogen detection based on fluorescence spectra.